The present invention relates to fine opening machinery for textile fibrous material. Textile fibers are delivered to the fine opening machinery by machinery such as, bale opening equipment or the like in the form of relatively large tufts. The fine opening machinery breaks these relatively large tufts into smaller tufts which are then delivered to other processing or opening machinery such as, lap formers or additional fine opening machinery for reducing the tufts to even smaller tufts.
The general purpose of fine opening machinery is to open the fibers as much as possible. It is desirable to break the fibrous mass which is fed to the fine opening machinery into tufts which are as small as possible. Fine opening machinery generally takes many forms. A typical arrangement is one which includes a chute for holding a reserve of fibers conveyed to the chute from machinery such as bale opening machinery. A feed element such as a pair of rolls is located at the bottom of the chute and forms a nip for drawing fibers thereinto and presenting them to a primary opening element such as a rotating cylinder which contains teeth or spikes on its outer surface. The relatively large tufts in the chute are drawn into the nip of the feed element and held while the teeth of the primary opening element combs the tufts and pulls off small individual tufts which are then conveyed to further processing machinery.
In other types of fine opening machinery, fibers are supplied to the feed elements by a substantially horizontal conveyor on which the unopened fibrous material is deposited and conveyed to the nip of the feed element.
The capacity of the fine opening machinery is measured in terms of mass flow rate of fibers for a given degree of fiber opening. The fibrous mass is delivered to the fine opening machinery at the rate at which machinery prior to opening can supply fibers. In the case of chute feeds, the chute must be of a size which provides a reserve capacity and insures that there will be a continuous and even flow of fiber to the feed element. To achieve this condition, the width of the chute is such so as to require the sidewalls to converge toward the feed element so that all of the fibers are conveyed and condensed to a point above the nip of the feed element as stock is fed down along the chute. The fibers are compressed as they are fed into the nip of the feed element. Although a great deal of compression can be tolerated, there are limits to how tightly the fibers can be held in the nip of the feed element or between the feed rolls if feed rolls are employed without damaging the fibers. In other words, there is a practical limit of mass flow rate of fibers for a given nip opening.
One solution to the above problem is to increase the nip opening of the feed element. This will increase the feed rate of fibers to the primary opening element. However, this has the disadvantage of allowing large tufts to slip through the feed element. These large tufts are "jerked through" by the primary opening element and consequently passed downstream in an unopened condition. The output of the fine opening machinery is increased but additional opening equipment may be needed downstream to further open the fibers.
A second solution is to increase the speed of the feed element. However, the degree of fiber opening is predicated upon the relative speed differential between the feed element and the primary opening element. Consequently, speedup of the feed element requires a proportional speedup of the primary opening element. This will increase the productive capacity of the fine opening machinery while maintaining a fine degree of opening. However, there are practical limitations to how fast this machinery can run without wear and damage. In most cases, the primary opening element is already running at its upper mechanical limit.
A third solution is to divide the flow of fiber which is fed to the fine opening machinery into two or more streams and employ two or more units of fine opening machinery. In this way, the productive capacity of each unit can be brought in to tolerable limits, however, the cost of employing double or triple the number of fine opening units is objectionable.
In fiber opening machinery which employs a chute as a storage or reserve, the expansive forces of the fibers create sidewalls friction which prevents the easy flow of fibers to the feed elements. Very often the feed elements will draw fibers from the center area of the chute and create a cavity because of the bridging capabilities of the fiber to the sidewalls. This may cause a temporary stop or erratic fiber feed to the primary opening element. One solution to this problem is to employ an upper set of rotating "bridge ruffling rolls" located above the feed element. This upper set of "bridge ruffling rolls" ruffles the fiber stock and helps to break up the bridge. It also condensed the fiber stock down to the feed element. Machinery of this type is illustrated in U.S. Pat. Nos. 3,552,800 and 3,851,925. One disadvantage of "bridge ruffling rolls" is that they force the fibers into the nip of the feed element which results in an undersirable nip pressure.